Problem :
It’s seems like a big problem. I can’t login as root, because I use the fedora20, and I can not use sudo. What can I do now ?
Solution :
su authentication failure, sudo missing
You can use
pkexec yum install sudo. pkexec will let you enter your password in your OS’s GUI.pkexec allows an authorized user to execute PROGRAM as another user.
If username is not specified, then the program will be executed as the
administrative super user, root.This helped:
https://askubuntu.com/questions/434525/can-sudo-be-reinstalled-after-being-removed
Source https://unix.stackexchange.com answer su authentication failure, sudo missing by portOdin